They have white on their leaves. They were given to me by a neighbor. I store them under my house, just like she does and bring them out in spring.
My Calla Lilies Don’t Bloom
Certified GKH Gardening Expert
This could be powdery mildew from being stored in a damp location.
Treat the plant with Neem Oil.
They also may need more Phosphorous to encourage flowering. Bone Meal is a good way to do so.
Here are some links that will help.